1. Field of the Invention
The present invention relates to movable body systems, pattern formation apparatus, exposure apparatus and exposure methods, and device manufacturing methods, and more particularly to a movable body system equipped with a movable body which moves holding an object, a pattern formation apparatus equipped with the movable body system, an exposure apparatus equipped with the movable body system and an exposure method in which an energy beam is irradiated on an object so as to form a predetermined pattern on the object, and a device manufacturing method using the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (electron devices and the like) such as semiconductor devices and liquid crystal display devices, exposure apparatuses such as a reduction projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a reduction projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are relatively frequently used.
In this kind of exposure apparatus, in order to transfer a pattern of a reticle (or a mask) on a plurality of shot areas on an object subject to exposure such as a wafer or a glass plate (hereinafter, generally referred to as a wafer), a wafer stage holding the wafer is driven in an XY two-dimensional direction, for example, by linear motors and the like. Position measurement of such a wafer stage was generally performed using a laser interferometer whose stability of measurement values was good for over a long time and had a high resolution.
However, requirements for a stage position control with higher precision are increasing due to finer patterns that accompany higher integration of semiconductor devices, and now, short-term variation of measurement values due to temperature fluctuation of the atmosphere on the beam path of the laser interferometer and/or the influence of temperature gradient has come to occupy a large percentage in the overlay budget.
Meanwhile, as a measurement unit besides the laser interferometer used for position measurement of the stage, an encoder can be used, however, because the encoder uses a scale, which lacks in mechanical long-term stability (drift of grating pitch, fixed position drift, thermal expansion and the like), it makes the encoder have a drawback of lacking measurement value linearity and being inferior in long-term stability when compared with the laser interferometer.
In view of the drawbacks of the laser interferometer and the encoder described above, various proposals are being made (refer to U.S. Pat. No. 6,819,425 description, Kokai (Japanese Patent Unexamined Application Publication) No. 2004-101362 bulletin and the like) of a unit that measures the position of a stage using both a laser interferometer and an encoder (a position detection sensor which uses a diffraction grating) together. Especially, encoders that have a measurement resolution nearly equal to or better than the laser interferometer have appeared (for example, refer to U.S. Pat. No. 7,238,931 description and the like) these days, and the technology to put the laser interferometer and the encoder described above together is beginning to gather attention.
However, in the case a mirror of the interferometer or a scale (such as a grating) of the encoder is arranged on the outside, such as, for example, on the side surface of a stage, a position (positional relation with a predetermined point on the stage) on the stage changes along with the minute deformation of the stage which occurs when the stage is accelerated, which makes the probability high of a decrease in the position measurement precision of the stage. Further, for example, from the viewpoint of improving throughput, even if a new technology was proposed of beginning exposure during the acceleration of the wafer stage in a scanning stepper, there is a risk that the change of the position of the mirror or the scale on the stage that accompanies the acceleration of the stage described above will become an obstacle factor when practicing the new technology.